With the advent of microwave ovens and the frequent cooking in such ovens of foods taken directly from a freezer, it is desirable to have a thermoplastic container which can be compactly stored in the freezer but which can also be used directly in a microwave oven. Rigid containers which stand upright are not always of the most compact shape for storage in the freezer, often taken up unnecessary room when not fully filled, and customarily require lid removal to allow venting during cooking. Thermoplastic storage and cooking bags which can be laid on their sides have the disadvantage that when opened for venting during cooking, spillage of product in the oven can result.
Since the introduction of microwave cooking, it has been desirable to have a compact plastic pouch which can stand upright sufficiently to avoid spillage, yet remain flexible enough so that the storage space beyond that of the product contained therein is essentially not required to be utilized in the freezer compartment. Gussetted bags are customarily laid on their sides when the product therein is being cooked, as illustrated in FIG. 4 of U.S. Pat. No. 3,851,574, for example. Compact freezing bags with a top opening are illustrated by U.S. Pat. No. 3,389,783, for example, but these have not been designed for venting or microwave cooking and are merely a flat, pillow-type package. Stand-up bags, such as typically illustrated in U.S. Pat. No. 3,799,914 or 3,380,646, are designed to contain food in their upright sections, which make the bags more readily upsettable if they were to be used in a microwave oven for cooking. Other packages designed to give wider bottoms for packaging, such as shown in U.S. Pat. No. 3,003,681, still are intended to contain the bulk of the product in the upright portion of the container, which does not make for most efficient stacking or cooking. The above containers have advantageous features which represent the state of the art prior to the present invention but which fail to include the improvements necessary to have a superior freezer to microwave oven bag which is compactable, yet non-spillable in a cooking environment.